Ammonium nitrate-hydrocarbon oil explosive composition



United States Patent Ofifice 3,240,641 Patented Mar. 15, 1966 This invention relates to a novel ammonium nitrate explosive. In another aspect, it relates to a method of preparing an ammonium nitrate explosive. In a further aspect, it relates to an improved method of producing an explosion.

The use of ammonium nitrate in admixture with fuel oil or diesel oil as a low-grade explosive is becoming increasingly widespread in open pit and underground mining, quarrying, seismic exploration, and construction of pipeline trenches, roads, railways, etc. Such an explosive can be readily prepared in small batches in the field or can be prepared on a large scale with bulk mixing equipment and stored or aged in warehouses.

The use of ammonium nitrate explosives of this type, usually consisting of a mechanical mixture of 94 Weight percent fertilizer-grade ammonium nitrate and 6 weight percent fuel oil or diesel oil, has encountered certain problems due to the nature of the oil component. The oils normally used in making such explosives have a volatility which causes a loss of oil from the mixture through volatilization of the oil component upon storage or transit of .the mixture. Such volatility gives rise to objectionable odor from the ammonium nitrate explosive mixture, particularly in confined areas where the mixtures are stored or used, for example warehouses and underground mines. The loss of oil from these mixtures prior to their use also causes a shift in the carbon-oxygen balance which adversely affects the total energy released when such explosives are detonated and an increase in the quantity of the toxic reddish-brown fumes (oxides of nitrogen), which fumes are particularly obnoxious and hazardous when such explosives are used in underground mines where the air or atmosphere must be closely controlled and kept as pure as possible. A further problem attendant the use of such oils in making ammonium nitrate explosives is the discoloration that many of these oils impart to the ammonium nitrate when mixed therewith, which discoloration detracts from the sales appeal of the oil and explosive made therewith.

Accordingly, an object of this invention is to provide an improved ammonium nitrate explosive composition. Another object is to provide a method of preparing such ammonium nitrate explosive composition. Another object is to prepare a method of genera-ting an explosion using such an explosive. Another object is to overcome the problems normally encountered when ammonium nitrate is mixed with fuel oil, diesel oil, or the like due to the volatility of such oils. Further objects and advantages of this invention Will become apparent to those skilled in the art from the following description and accompanying claims.

I have now discovered an improved ammonium nitrate explosive can be prepared by admixing particulate ammonium nitrate with a normally liquid hydrocarbon oil meeting the following specification:

Pour point, F. maximum 50 Flash point, F. minimum 250 Viscosity, SUS at F 30 to API gravity 24 to 45 ASTM col-or 3 Aromatics, acid treated, volume percent 30 Sulfur content, weight percent 2 Nitrogen content, weight percent 0.1 Bromine number 2 Ammonium nitrate explosives made with oils meeting such specifications exhibit little if any loss of the oil component at the ambient conditions normally encountered by ammonium nitrate explosives. As a result, little if any obnoxious and potentially hazardous oil vapors or odor will be encountered in the preparation, storage, transit, or use of such explosives, and the carbon-oxygen balance necessary to realize the desired blasting or explosive properties of the explosive will not be disturbed. The explosives of this invention are relatively low in cost and can be readily prepared in the field or on a large scale for use in any of the aforementioned mining, construction, etc.

The ammonium nitrate used in preparing the explosives of this invention is particulate in form, e.g., granules, prills, etc. I prefer to use it in the form of prills, such as that prepared by spraying hot ammonium nitrate from the top of the tower and allowing the droplets to descend in a countercurrent stream of air at a lower temperature and form porous aggregates or prills of microcrystals, usually about to of an inch in diameter. Such prills can be coated, if desired, with suitable conditioning agents to improve their storage stability, such as diatomaceous earth, kaolin, etc. An especially useful conditioning agent is an admixture of kaolin and a small amount of an alkylaryl sulfonate, e.g., Petro-Ag. The ammonium nitrate can be of fertilizer grade with a size of 10 to 14 mesh (U.S. sieve).

The ammonium nitrate is mechanically mixed with any one or a mixture of the oils meeting the specification set forth above, these oils being available from many petroleum refinery streams. Any suitable mixing technique can be used, such as that currently being employed for ammonium nitrate-fuel oil or ammonium nitrate-diesel oil explosives. For example, such mixing can be done in the field or on the job in small batches in a tub or other suitable container and the mixture then poured in a bore hole, or the oil can be sprayed on the ammonium nitrate as it flows through a funnel into the bore hole, or the oil can be poured in open bags of the ammonium nitrate and used as prepared or after several hours or days to allow the oil to diffuse into the ammonium nitrate. Alternatively, large batches can be prepared with bulk mixing equipment and the mixture stored or aged before use. The relative amounts of ammonium nitrate and oil used in making the explosives of this invention .are the same as that now generally used to make ammonium nitrate explosives. Broadly, the ammonium nitrate is mixed with at least a stoichiometrically equivalent amount of the oil. Generally, the improved explosives of this invention will comprise 2 to 8 Weight percent of the specified oil and from about 92 to 98 weight percent ammonium nitrate, based on the total Weight of the exploup I sive. Preferably, the explosive will contain from about 4 to 6 weight percent of the specified oil and 94 to 96 weight percent of the ammonium nitrate. These two components, the oil and ammonium nitrate, are the only essential components of the explosives of this invention; however, other materials normally used or found in ammonium nitrate-diesel oil explosives can be incorporated, such as the aforementioned ammonium nitrate conditioning agents, e.g., to prevent caking, sensitizers, e.g.

The detonation of the ammonium nitrate explosives of this invention, which are cap-insensitive, can be accomplished by any of the conventional techniques now used for detonating ammonium nitrate explosives. For ex ample, detonation can be accomplished with a high explosive primer or booster, such as one or more sticks of dynamite, attached to a line of Primacord or other detonating fuse or to a high power electrical cap, e.g., No. 8 cap.

The objects and advantages of this invention are further illustrated in the following examples, but it should be understood that the various details of these examples are not to be construed to unduly limit this invention.

EXAMPLES A series of runs were carried out in which mixtures of prilled ammonium nitrate and various oils were formed and subjected to certain evaluation tests. The ammonium nitrate used was fertilizer-grade prills. In each run, 94 parts by weight of the prilled ammonium nitrate was mechanically mixed with 6 parts by weight of the candidate oil. The ammonium nitrate-oil mixtures were allowed to stand until the oil had been absorbed on the prilled ammonium nitrate, and a portion of each of the mixtures was sealed in a closed bottle and stored at room temperature, approximately 72 to 76 F. From time to time the bottle was opened and the presence or absence of odor, and its strength, above the explosive mixture was rated. At the same time, the color of the mixture was observed and rated. A sample of each mixture was also tested for loss of oil by evaporation. In this latter test, 100 g. of the mixture was placed in a pan so as to have a bed depth of about inch and an exposed area of about 20 square inches. Air at about 76 F. was then blown across the bed at about 300 linear feet per minute. The weight percent of the oil lost from the sample at the end of 15, 45, 75 and 100 hours was determined,

The specification of the oils used in these tests is given below in Table I, while the results of these evaluation tests are shown below in Table II.

Table I Oil sample P ur point, F., max- +10 +5 +10 +35 Flash point, F.. mm. 270 390 300 150 285 380 Viscoslty, SUS 100 F 55-65 97. 3 48. 1 33-40 50. 9 1 45. 1 API gravlty 25. 3 33. 0 33. 6 35-40 41. 5 13. 6 ASTM color 2 1 0.5 2 0. 5 8 Aromatics, acid treated,

vol. percent 26. 7 3. 6 8. 6 21. 7 14. 7 S1. 5 Sulfur, Wt. percentl. 54 0. 06 0. 22 0. 18 0. 06 0. 79 Nitrogen, wt. percent 0.02 0.006 0.006 0.007 0. 007 0.15 Bromine No 1. 1 0. 2 0. 8 1. 7 7. 5 29 1 This viscosity is given 210 F.

Table II Wt. percent of oil lost (cumula- Odor of Color of tive) from mixture after- Run mixture 1 mixture 2 15 hrs. 45 hrs. hrs. hrs.

0 1 0. 8 1. 9 2. 5 3. 0 0 l 0 0 0 0. 1 0 1 0. 2 O. 5 1. O 1. 2 3 l 9 17 22 24. 5 3 1 1. 5 3. 5 4. 0 4. 2 2 3 0 0 0 0. 1

1 Odor rating of 0 means no odor detected, while a rating of 3 means strong odor detected.

2 Color rating of 1 means no discoloration, and color rating of 3 means nitrate was highly discolored.

Various modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing description and examples, without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be limited unduly to that set forth herein for illustrative purposes.

I claim:

1. An explosive composition comprising in admixture ammonium nitrate and oil meeting the following specification:

Pour point, F. maximum 50 Flash point, F. minimum 250 Viscosity, SUS at 100 F. 30 to API gravity 20 to 45 ASTM color 3 Aromatics, acid treated, vol. percent 30 Sulfur content, wt. percent 2 Nitrogen content, wt, percent O.l Bromine number 2 2. An explosive composition comprising in admixture 92 to 98 weight percent prilled ammonium nitrate and 2 to 8 weight percent of oil meeting the following specification:

Pour point, F. maximum 50 Flash point, F. minimum 250 Viscosity, SUS at 100 F. 30 to 125 API gravity 20 to 45 ASTM color 3 Aromatics, acid treated, vol. percent 30 Sulfur content, wt. percent 2 Nitrogen content, wt. percent 0.1 Bromine number 2 3. The explosive composition of claim 2, wherein said ammonium nitrate is 94 to 96 weight percent and said oil is 4 to 6 weight percent.

References Cited by the Examiner UNITED STATES PATENTS 3,046,887 7/1962 Brinkley et al. 14960 X 3,068,791 12/1962 Lambert et al. 102-23 3,103,457 9/1963 Grossmann 14946 3,111,437 11/1963 Hino et a1 14946 3,119,332 1/1964 Grebe et al. 102-23 3,129,128 4/1964 Berczely 14946 CARL D. QUARFORTH, Primary Examiner.

BENJAMIN R. PADGETT, BENJAMIN A. BOR- CHELT, Examiners. 

1. AN EXPLOSIVE COMPOSITION COMPRISING IN ADMIXTURE AMMONIUM NITRATE AND OIL MEETING THE FOLLOWING SPECIFICATION: 